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nebular hypothesis |
Also found in: Wikipedia, Hutchinson | 0.01 sec. |
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nebular hypothesis: see solar system solar system, the sun and the surrounding planets, natural satellites , dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. ..... Click the link for more information. . nebular hypothesis [′neb·yə·lər hī′päth·ə·səs] (astrophysics) A theory, proposed in 1796 by Laplace, supposing that the planets originated from the solar nebula surrounding the proto-sun; as the sun cooled, it contracted, rotated faster, and thus caused a ringlike bulging at the equator; this bulge eventually broke off and formed the planets; Laplace further theorized that the sun and other stars formed from clouds of nebulous matter; the theory in this form is not accepted. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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| The presumed planet's youth challenges the conventional model of planetary formation, in which dust around a star gathers into ever-larger rocks that crash together and eventually accrete into planets. Among the projects in the planning stages are: a trip to Mars to retrieve soil samples and bring them back to Earth, a rendezvous with Pluto, an infrared telescope to examine star and planetary formation, a mission to Jupiter's mysterious moon Europa, a trip to retrieve samples from comets, and missions to look for planetary systems resembling the solar system. A previous analysis of similar data suggested the core took 60 million years to take shape, but the new estimates are in accord with several other lines of evidence, as well as the widely accepted theoretical models of planetary formation. |
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